Can I use Instrumentation Amplifier in this application?

Hi shurp,

May I know what application are you trying to design? Can you elaborate what is the nature of your input? (Is it from an ac line or a sensor, voltage level, frequency, etc.) From your block diagram, may I know what is the purpose of your diff amp in the first block? Also is your system connecting to a converter after the InAmp stage here in the block diagram or does your microcontroller have an internal converter already?

You may want to check this article if any application circuit here matches your application: Instrumentation Circuitry Using RMS-to-DC Converters.

Regards,

Kristine

kristinehoffman I hope the respond below answers what you wanted to know. Please let me know if there is any type of instrumentation amplifier that works well.  

Hi shurp,

Could you share what is the amplitude of your input signal and what your operating frequency and required gain is? Also in your block diagram in the first stage, do you mean difference amplifier? differential amplifiers are usually used as ADC drivers. If you're using a Wheatstone bridge, usually In-Amps are used to cancel out the high common-mode voltage from the Wheatstone bridge although a difference amplifier would also make sense in your block diagram especially if the common-mode voltage exceeds supply level. Using In-Amps will also let you have a large gain and filtered signal due to the bandwidth limiting. If you like to filter out your signal more, you can add filters after the RMS to DC converter to simplify your circuit. I would recommend Wheatstone bridge > In-Amp > LTC1968 > Filter(optional) > ADC, but this will still depend if your specs would match this signal chain.

You may want to check AD8422 as it's typical application circuit has a Wheatstone bridge. 

It would be helpful for us to suggest a part for you if you can share in detail (with defined specs) the signal conditioning that you will be doing (example: Wheatstone bridge > in-amp (5Vin, 1kHz, G=10, etc.) > RMS to DC > filter (BW, etc.). If possible block per block explanation would be great!

Regards,

Kristine

Hi shurp,

Could you share what is the amplitude of your input signal and what your operating frequency and required gain is? Also in your block diagram in the first stage, do you mean difference amplifier? differential amplifiers are usually used as ADC drivers. If you're using a Wheatstone bridge, usually In-Amps are used to cancel out the high common-mode voltage from the Wheatstone bridge although a difference amplifier would also make sense in your block diagram especially if the common-mode voltage exceeds supply level. Using In-Amps will also let you have a large gain and filtered signal due to the bandwidth limiting. If you like to filter out your signal more, you can add filters after the RMS to DC converter to simplify your circuit. I would recommend Wheatstone bridge > In-Amp > LTC1968 > Filter(optional) > ADC, but this will still depend if your specs would match this signal chain.

You may want to check AD8422 as it's typical application circuit has a Wheatstone bridge. 

It would be helpful for us to suggest a part for you if you can share in detail (with defined specs) the signal conditioning that you will be doing (example: Wheatstone bridge > in-amp (5Vin, 1kHz, G=10, etc.) > RMS to DC > filter (BW, etc.). If possible block per block explanation would be great!

Regards,

Kristine